type token =
  | TokenStr of (string)
  | TokenColon
  | TokenIf
  | TokenFi
  | TokenTo
  | TokenGoto
  | TokenTrue
  | TokenFalse
  | TokenLBr
  | TokenRBr
  | TokenAnd
  | TokenOr
  | TokenNot
  | TokenSkip
  | TokenEof

val main :
  (Lexing.lexbuf  -> token) -> Lexing.lexbuf -> Syntax.nba
